1. Field of the Invention
The present invention relates to computer systems with multiple peripheral devices such as printers and video displays. More particularly, the invention concerns an apparatus, article of manufacture, and method in which a computer system automatically senses characteristics of a potentially diverse assortment of attached peripheral devices and maximizes the communications speed between these the devices and a central controller.
2. Description of the Related Art
Many offices today utilize computer systems with a centralized processing unit and distributed peripheral devices. This is often a cost effective approach, because multiple users can share one expensive, powerful central processing unit ("CPU"). Individual users may have their own inexpensive components, such as graphical interfaces and printers. These components are typically coupled to the CPU by connecting cable, which may be tens, hundreds, or even thousands of feet long.
In some systems with distributed-peripherals, the devices are coupled to communications ports of the CPU. Each port may be used by one device alone, or shared by multiple devices. With a "point-to-point" arrangement, a port is used by one device. With a "cable thru" configuration (also called "multi-drop"), a port may be shared by multiple devices, connected in daisy chain fashion. An exemplary protocol for communications between a CPU and distributed peripheral devices is the IBM 5250 Twinaxial protocol (called "Twinax").
For many applications, known distributed-peripheral arrangements are completely satisfactory. However, competition in the industry spurs engineers to constantly seek improvements to these systems. Communication speed is one design feature that is important to engineers and customers alike. Faster communications between a CPU and its peripheral devices leave more time for the CPU and peripheral devices to complete their respective jobs. It also means that the customer does not have to wait as long for data or images to be transferred between the CPU and peripheral device
Usually, however, the communications port and its attached peripheral devices are built to communicate at one pre-established, fixed rate. Thus, improvements in communications speed are only possible by upgrading the communications port and the peripheral devices. Components that use the current Twinax protocol, for example, communicate at one million bits per second (i.e., 1 Mbps). For some users, it may be prohibitively expensive to upgrade components very often. Furthermore, it may be difficult to keep track of which components have which levels of communication speed.